See https://github.com/chrippa/livestreamer/blob/develop/CHANGELOG.rst
It's a matter of renaming the ebuild to livestreamer-1.8.0.ebuild. Nothing else needed.
+*livestreamer-1.8.0 (04 May 2014) + + 04 May 2014; Markos Chandras <hwoarang@gentoo.org> +livestreamer-1.8.0.ebuild: + Version bump. Bug #508822 +